Small interfering RNA (siRNA) is a short double stranded RNA. It behaves like a mediator of the RNA interference phenomenon silencing the specific gene expression by triggering the cleavage of a target messenger RNA (mRNA) at post-transcriptional level in the cytoplasm (Hamilton, et al., Science 1999; Elbashir, et al., Nature (2001)). siRNA is a powerful tool to control cellular processes at a post-transcriptional level. Its great potency is due to the high sequence-specific inhibition efficiency (Novina et al., Nature (2004) 430:161-164). Thus, siRNA strategy has been strongly considered for the down-regulation of certain proteins in the areas of functional genomies and genomic therapeutics.
Although siRNA has been used as a therapeutic agent for various genetic diseases, its therapeutic application is still limited because of its instability against nucleases. Thus, what is needed are siRNA molecules that are more stable, and thus more active and useful as therapeutic agents.